A data simulation study comparing the one-high-threshold (1HT) and two-high-threshold (2HT) multinomial models suggested that 2HT models are more likely to misestimate the underlying parameter values, due to inflation of some parameters (b and d), and deflation of others (D).
Menon, Mahesh and Woodward, Todd S.
"A Comparison of One-High-Threshold and Two-High-Threshold Multinomial Models of Source Monitoring,"
Journal of Modern Applied Statistical Methods: Vol. 6
, Article 26.
Available at: http://digitalcommons.wayne.edu/jmasm/vol6/iss1/26